There are many forms of fracturing being used and one of those methods is known as plug and perforate. In this method a zone that has already been treated is isolated with a plug and a perforating gun is released from the plug and repositioned for perforating. With the zone previously treated now isolated with the plug the newly perforated zone can be fractured through the newly made perforations above the plug.
The plug designs in the past have involved dropping or pumping a ball onto a seat from surface after the guns are out of the hole, in one form of plug valve. The problem with this design is that it takes time and water to get the ball pumped to the seat.
Other valve designs for frac plugs have been proposed to avoid sending down a ball to land in a seat. These designs involve a caged ball that lifts off a seat when the gun is advanced with the cage retaining the ball. Flow in the downhole direction seats the ball on the seat to prevent flow. This means if the gun fails to fire there is no way to use flow to deliver a replacement gun as any such flow in the downhole direction seats the ball on the seat.
Yet other types of spring biased check valves have been suggested but they too will shut with flow in the downhole direction leaving the same problem of how to run in a replacement gun if the original gun fails to fire.
U.S. Pat. No. 5,564,471 illustrates a fuel delivery breakaway valve that closes off flow in the hose that separates with a car that drives off and blocks flow out of the hose remnant going back out as well as blocking flow out of the portion still attached to the pump. The opposed check valves are actuated with physical separation of the housing. Automobile fuel nozzles also have a valve member that is resettable that is actuated by backpressure from the tank being filled to avoid overfilling the gas tanks while then resetting to allow pumping additional fuel.
U.S. Pat. No. 6,394,180 shows a ball sitting on a spring with a covering cage to retain the ball to a frack plug. On increase in flow the ball compresses the spring to land on the seat until the flow is reduced and the spring can then raise the ball off the seat to reopen the passage. The ball is not retained in the uphole direction until it hits the surrounding cage. This design has the potential problem of the ball jamming around the spring rather than seating off on the seat for a clean seal. Other problems include; 1. Springs are made of hardened steel and aren't easily millable. Quick mill-out time is essential. 2. The force on the ball due to flow will change as it moves in the passage due to compressing the spring. This adds variability to the predetermined flow rate to close the valve.
What is needed and addressed by the present invention is a valve for a plug in a plug and perforate context that is disposed in the plug and has a selectively secured valve member that allows bypass flow and remains in the open position if the gun fails to fire so that a replacement gun can be run in with flow through the open valve. The plug member is selectively released with raising the flow rate through the plug to release the valve member to land on its seat to allow subsequent fracturing or other treatments such as stimulation or acidizing, for example. A backup seat is provided for dropping an object if for any reason the plug member fails to release and move to its seat. These and other aspects of the present invention will be more readily apparent from a review of the description of the preferred embodiment and the associated Figure while recognizing that the full scope of the invention is to be determined by the appended claims.